Resistance, accumulation and transformation of selenium by the cyanobacterium Synechocystis sp. PCC 6803 after exposure to inorganic Se^VI or Se^IV

Abstract

Our purpose was to investigate the ability of Synechocystis sp. PCC 6803, a photosynthetic prokaryote isolated from fresh water, to resist, incorporate and reduce the oxidized forms of selenium including selenite and selenate, the major selenium species present in aquatic systems. Selenium speciation and the chemical intermediates during selenium transformation were determined by X-ray absorption near edge structure (XANES) spectroscopy. The possible internalisation pathways involving selenium and the metabolic fate of selenate and selenite were examined. Selenate metabolism seemed to proceed via the sulfate reduction pathway resulting in the formation of the R-Se-H, R-Se-R and R-Se-Se-R species. The transformation of selenate to toxic amino acids may explain the high sensitivity of Synechocystis to selenate. Several mechanisms of selenium reduction seem to compete during selenite assimilation. A specific mechanism may transform internalised selenite into selenide and, subsequently induce the biosynthesis of selenoproteins. A non-specific mechanism may interfere with thiols, such as glutathione in the cell cytoplasm, or with proteins in the periplasm of the bacteria, notably thioredoxins. Several hypotheses concerning the complex transformation of selenium in Synechocystis could therefore be proposed.

Selenium cannot substitute for sulfur in cell density‐independent bioluminescence in Vibrio fischeri

“…Indeed, various studies have demonstrated that selenate uptake in some microorganisms, such as E. coli , yeast , and Synechocystis sp. , is mediated by a sulfate transporter. Therefore, when the metabolized sulfur in transferred onto an organic moiety such as L‐cysteine or L‐cystine, competition between sulfur and selenium does not occur.…”

High-resolution spectroscopy on an X-ray absorption beamline

“…The amounts correspond to mg g À1 (name of the element in bold) or mM l À1 (italic). These experimental concentration limits are obtained during EXAFS studies except for the Se, V and two of the Cr experiments (Chaurand et al, 2007;Rose, Cornu et al, 2007;Gouget et al, 2005; XANES studies). Open circles: Bakkaus et al 2009 experiments presented in this paper the Si(444) reflection was chosen.…”

Fungal Selenium(VI) Accumulation and Biotransformation—Filamentous Fungi in Selenate Contaminated Aqueous Media Remediation

“…The cyanobacterium Synechocystis sp. accumulated almost 10% of initial 0.3 mg L −1 selenate concentration, and selenite accumulation reached almost 34% without selenium volatilization . Kagami et al reported efficient selenium(VI) biovolatilization by bacterium Pseudomonas stutzeri under aerobic conditions.…”